FR3100283A1 - COUPLE CONVERGENT-DIVERGENT FLAP FOR VARIABLE GEOMETRY TURBOREACTOR NOZZLE WHOSE DIVERGENT FLAP INCLUDES A COOLING AIR EJECTION DUCT - Google Patents

Abstract

In a converging flap-divergent flap pair (52B) for a nozzle (28) of a variable-geometry convergent-divergent turbojet type, the converging flap (40B) comprises a cooling air circulation duct (70), and the flap divergent (42B) has a cooling air ejection duct (78) connected to the cooling air circulation duct (70) for receiving cooling air from the latter, and configured to eject the cooling air. cooling air along an internal surface of the flue gas line (66) of the diverter flap (42B). Figure for the abstract: Figure 4

Description

CONVERGENT FLAP-DIVERGENT FLAP PAIR FOR VARIABLE GEOMETRY TURBOJET NOZZLE WHERE THE DIVERGENT FLAP COMPRISES A COOLING AIR EXHAUST DUCT

The present invention relates to the field of turbojet engines intended for the propulsion of aircraft capable of supersonic flight, and relates more particularly to a converging flap-diverging flap couple for a turbojet nozzle of the convergent-divergent type with variable geometry, a nozzle equipped with such a converging flap-diverging flap pair, and a turbojet comprising such a nozzle.

STATE OF THE PRIOR ART

Turbojet engines intended for supersonic flight generally include a postcombustion channel whose outlet is delimited by an axisymmetric nozzle of the convergent-divergent type, in order to allow the acceleration of the air flow leaving the engine at speeds greater than Mach 1.

To be effective at the different speeds at which a supersonic aircraft is likely to fly, such a nozzle has a variable geometry, making it possible to vary the internal section of the nozzle and in particular the position and the shape of the neck of the nozzle.

To this end, such a nozzle comprises a set of movable internal flaps intended to channel the flow of gas leaving the reactor, this assembly comprising an annular row of convergent flaps followed by an annular row of divergent flaps. The divergent flaps are generally articulated at their respective upstream ends on respective downstream ends of the convergent flaps, and the convergent flaps are themselves articulated at their respective upstream ends on a stator structure of the turbojet engine. The set of mobile internal flaps therefore consists of an annular row of convergent flap-divergent flap pairs.

Such a nozzle further comprises an annular row of movable external flaps surrounding the set of movable internal flaps.

Given the high temperature of the gases leaving a postcombustion channel, it is desirable to cool the internal flaps of such a nozzle in order to guarantee their mechanical strength.

For this purpose, cooling air must be taken from the working air flow of the turbojet engine, which is why it is desirable to limit the quantity of air necessary for cooling in order to optimize the propulsion performance of the engine.

Such an objective is however in contradiction with the wish to increase the richness of the gases in postcombustion to improve the propulsive performances of the turbojet engines, since such an increase in richness implies an increase in the temperature of the gases, and therefore an increase in the need in cooling.

The object of the invention is in particular to at least partially solve the above problem, and in particular to propose an effective solution for cooling the internal movable flaps of a convergent-divergent nozzle with variable geometry of a turbojet engine, while limiting the negative impact of such cooling on the propulsion performance of the turbojet engine.

The invention proposes for this purpose a converging flap-diverging flap pair for a turbojet nozzle of the convergent-diverging type with variable geometry, comprising a convergent flap, and a divergent flap mounted to pivot on the convergent flap about a pivot axis, whereby the converging flap-diverging flap couple is capable of passing from a first extreme angular configuration, in which the converging flap and the diverging flap form between them a maximum salient angle, to a second extreme angular configuration, in which the converging flap and the diverging flap form between them a minimum salient angle less than the maximum salient angle,
wherein the converging flap comprises a respective inner wall, having a respective combustion gas channeling inner surface and a respective outer surface, and a respective outer wall,
in which the converging flap comprises a respective cooling air circulation duct defined between the respective external surface of the respective internal wall of the converging flap, and the respective external wall of the converging flap,
wherein the diverging flap has a respective flue gas channeling wall, having a respective flue gas channeling inner surface and a respective outer surface, and
wherein the diverging flap further comprises a respective cooling air ejection duct connected to the respective cooling air circulation duct of the converging flap to receive cooling air therefrom, and configured to eject the cooling air along the respective combustion gas channeling inner surface of the respective combustion gas channeling wall of the diverging flap.

The invention thus allows effective cooling of mobile internal flaps, requiring only a moderate quantity of air, and therefore having a moderate impact on the performance of a turbojet engine equipped with such a nozzle.

The invention thus makes it possible to improve the mechanical strength of mobile internal shutters and to control the thermal behavior of the latter.

The invention also makes it possible to limit the temperature of such a nozzle, and therefore to limit the infrared signal thereof.

Limiting the temperature of the nozzle also allows the use of a wider choice of materials within it, in particular electromagnetic absorption materials which are generally not very tolerant of high temperatures.

Preferably, the respective cooling air ejection duct of the divergent flap comprises a respective connection portion cooperating by fitting with a respective end portion of the respective cooling air circulation duct of the convergent flap so as to ensure the connection of the respective cooling air ejection duct of the diverging flap to the respective cooling air circulation duct of the converging flap.

Preferably, the respective cooling air ejection duct of the diverging flap comprises an air outlet portion arranged in the extension of the connection portion and having an air outlet section remote from a downstream end of the respective combustion gas ducting wall of the diverging flap to eject the cooling air along the respective combustion gas ducting inner surface of the respective combustion gas ducting wall of the diverging flap.

Preferably, the respective outer wall of the convergent flap comprises a respective end portion which delimits a downstream part of the end portion of the respective cooling air circulation duct of the convergent flap, and which is in the form of a portion of axis cylinder merging with the pivot axis.

Preferably, the respective combustion gas channeling wall of the diverging flap comprises a respective end portion, which delimits the connection portion of the respective cooling air ejection duct of the diverging flap, and which is of complementary shape to the respective end portion of the respective outer wall of the converging flap, such that the respective end portion of the respective combustion gas channel wall of the diverging flap slides along or moves opposite , the respective end portion of the respective outer wall of the convergent flap, when the convergent flap-divergent flap pair passes from one to the other of the first and second extreme angular configurations.

Preferably, the connection portion of the respective cooling air ejection duct of the divergent flap is engaged in the end portion of the respective cooling air circulation duct of the convergent flap.

Preferably, the air outlet portion of the respective cooling air ejection duct of the diverging flap comprises or forms a sonic throat.

Preferably, the respective external wall of the convergent flap comprises a bulge adjacent to the end portion of the respective external wall of the convergent flap, the bulge being of reverse concavity with respect to the respective end portion of the respective external wall of the convergent flap, and the bulge delimiting an upstream part of the end portion of the respective cooling air circulation duct of the convergent flap.

Preferably, the converging flap further comprises a multi-perforated plate extending between the respective internal wall and the respective external wall of the converging flap, and provided with impact cooling orifices.

Preferably, the respective cooling air circulation duct of the converging flap comprises a cooling air circulation cavity, defined between the respective external wall of the converging flap and the multi-perforated plate.

Preferably, the respective cooling air circulation duct of the converging flap comprises an impact cooling cavity defined between the multi-perforated plate and the respective external surface of the respective internal wall of the converging flap, to allow cooling of the internal wall respective of the converging flap by impact of air jets formed through the impact cooling orifices from air circulating in the cooling air circulation cavity.

Preferably, the convergent flap comprises two respective opposite lateral end walls each connecting the respective internal wall of the convergent flap to the respective external wall of the convergent flap so that the two lateral end walls delimit between them the circulation duct d respective cooling air of the converging flap.

Preferably, the converging flap comprises a closing wall connecting the multiperforated plate of the converging flap to the respective internal wall of the converging flap so as to close an upstream end of the impact cooling cavity.

The invention also relates to a nozzle of the convergent-divergent type with variable geometry for a turbojet, comprising convergent-divergent flap pairs distributed around an axis of the nozzle and of which at least some are convergent-divergent flap pairs of the type described above, and a combustion gas circulation channel delimited at least by the respective internal combustion gas channeling surfaces of the respective internal walls of the respective convergent flaps and of the respective divergent flaps of the convergent flap-divergent flap pairs of the type described above.

The invention also relates to a turbojet engine for an aircraft, comprising a post-combustion channel surrounded by a cooling plenum separated from the post-combustion channel by a thermal protection jacket, and a nozzle of the type described above, in which the circulation cavities respective cooling air of the convergent flaps of the convergent flap-divergent flap pairs of the type described above of the nozzle are connected to the cooling plenum surrounding the postcombustion channel.

The invention will be better understood, and other details, advantages and characteristics thereof will appear on reading the following description given by way of non-limiting example and with reference to the accompanying drawings in which:

is a diagrammatic half-view in axial section of a turbojet comprising a nozzle of the convergent-divergent type with variable geometry, arranged at the outlet of a postcombustion channel;

is a diagrammatic half-view in axial section of a postcombustion channel and of a nozzle of the convergent-divergent type with variable geometry of a known type;

is a partial schematic perspective view of an annular row of diverging flaps forming part of the nozzle of FIG. 2;

is a partial schematic view in axial section of the variable geometry convergent-divergent type nozzle of the turbojet of FIG. 1, comprising convergent-divergent flap pairs according to a preferred embodiment of the invention, one of which is visible in a first configuration;

is an enlarged view of part of Figure 4;

is an even larger scale view of part of Figure 4;

is a view similar to FIG. 5A, illustrating the converging flap-diverging flap couple in a second configuration;

is a partial schematic perspective view of a convergent-divergent flap pair according to a preferred embodiment of the invention, which forms part of the nozzle of the convergent-divergent type with variable geometry of FIG. 4;

is a partial schematic perspective view of the converging flap-diverging flap couple of FIG. 6, in a disassembled state;

is a schematic top view of a multi-perforated plate belonging to the convergent flap of the convergent flap-divergent flap couple of figure 6.

In all of these figures, identical references may designate identical or similar elements. Moreover, these figures respect neither the scale nor the proportions of the elements which are represented there.

Detailed Statement Of Preferred Embodiments

FIG. 1 illustrates a turbojet engine 10, for example a two-spool, turbofan engine, intended for the propulsion of an aircraft capable of supersonic flight, and therefore intended in particular to be installed in the fuselage of such an aircraft.

Throughout this description, the axial direction X is the direction of the longitudinal axis 11 of the turbojet. Except where otherwise stipulated, the radial direction R is at all points a direction orthogonal to the longitudinal axis 11 and passing through the latter, and the circumferential direction C is at all points a direction orthogonal to the radial direction R and to the longitudinal axis 11. Unless otherwise stated, the terms "internal" and "external" respectively refer to a relative proximity, and a relative remoteness, of an element with respect to the longitudinal axis 11 Finally, the qualifiers "upstream" and "downstream" are defined by reference to a general direction D of the gas flow in the turbojet engine 10.

Such a turbojet engine 10 comprises, by way of illustration, from upstream to downstream, an air inlet 12, a low pressure compressor 14, a high pressure compressor 16, a combustion chamber 18, a high pressure turbine 20, a low-pressure turbine 22, a postcombustion channel 26, and a nozzle 28 of the convergent-divergent type with variable geometry. These members of the turbojet are all centered along the longitudinal axis 11 of the turbojet.

As is well known, the high pressure compressor 16, the combustion chamber 18, and the high pressure 20 and low pressure 22 turbines define a primary stream PF. The latter is surrounded by a secondary stream SF of the turbomachine which extends from upstream to downstream from an outlet of the low pressure compressor. Thus, in operation, the air F1 which has entered through the air inlet 12 and which has been compressed by the low pressure compressor 14, is then divided into a primary flow F2 which circulates in the primary stream and into a secondary flow F3 which circulates in the secondary stream 30. The primary flow F2 is then further compressed in the high pressure compressor 16, then mixed with fuel and ignited in the combustion chamber 18, before undergoing expansion in the high pressure turbine 20 then into the low pressure turbine 22.

The gas flow F4, consisting of the mixture of combustion gases from the primary stream and the secondary flow F3, then circulates in the post-combustion channel 26, then escapes from the turbojet engine 10 through the nozzle 28.

In operating mode with post-combustion, for example to propel an aircraft at supersonic speeds, fuel is mixed with the flow of gas F4 within the post-combustion channel 26, and the mixture thus formed is ignited within this post-combustion channel, to generate additional thrust. The convergent-divergent configuration of the nozzle 28 then makes it possible to accelerate the flow of gas F4 to supersonic speeds.

Figure 2 illustrates on a larger scale the postcombustion channel 26, and the nozzle 28, in a configuration known from the prior art.

The postcombustion channel 26 comprises an outer casing 32 in the shape of a revolution, and a thermal protection jacket 34 extending coaxially to the outer casing 32 inside the latter. The outer casing 32 and the thermal protection jacket 34 delimit between them a cooling plenum 36 intended for the circulation of a flow of cooling air CF1 along the outer casing 32.

The nozzle 28 comprises a set 38 of movable internal flaps externally delimiting a combustion gas circulation channel 39, which corresponds, within the turbojet engine, to a downstream end part of the postcombustion channel 26. The movable internal flaps thus allow to channel the flow of gas F4 at the outlet of the turbojet engine 10 in operation.

The assembly 38 of mobile internal flaps comprises, upstream, an annular row of convergent flaps 40, followed, downstream, by an annular row of divergent flaps 42.

The divergent flaps 42 are articulated, at their respective upstream ends 44, respectively on respective downstream ends 46 of the convergent flaps 40. The convergent flaps 40 are themselves articulated at their respective upstream ends 48 on a stator structure 50 of the turbojet engine.

The assembly 38 of movable internal flaps therefore consists of an annular row of convergent flap-divergent flap pairs 52, the flaps of each pair being articulated to be able to pass from a first extreme angular configuration, in which the convergent flap and the diverging flap make between them a maximum salient angle, at a second extreme angular configuration, in which the converging flap and the diverging flap make between them a minimum salient angle less than the maximum salient angle, and vice versa, in a manner known in itself.

For example, assembly 38 comprises controlled convergent flap-divergent flap pairs 52A, and follower convergent flap-divergent flap pairs 52B, arranged alternately in the circumferential direction C. The controlled convergent flap-divergent flap pairs 52A consist of convergent controlled flaps 40A and divergent controlled flaps 42A, while the convergent flap-divergent follower flap 52B pairs consist of convergent follower flaps 40B and divergent follower flaps 42B. FIG. 3 shows divergent flaps 42A, 42B respectively of controlled pairs 52A and following pairs 52B.

The controlled torques 52A, one of which is visible in FIG. 2, are directly connected to respective actuating members 54 of the nozzle, which actuating members are mounted on the stator structure 50 of the turbojet engine, so as to control directly the displacement of the ordered couples 52A. The following pairs 52B cooperate with the adjacent controlled pairs 52A via drive members (not visible in the figures) configured to communicate a movement of the controlled pairs 52A to the following pairs 52B.

The converging flaps 40 each comprise a respective combustion gas channeling wall 56, extending in a respective longitudinal direction of the flap, and having, on a radially internal side, a respective internal combustion gas channeling surface 58, and, on a radially outer side, a respective outer surface 59.

The divergent flaps 42 each comprise a respective combustion gas channeling wall 64, extending in a respective longitudinal direction of the flap, and having, on a radially internal side, a respective internal combustion gas channeling surface 66, and, on a radially outer side, a respective outer surface 67.

The internal combustion gas channeling surfaces 58 and 66 respectively of the convergent flaps 40 and the divergent flaps 42 delimit the combustion gas circulation channel 39, and therefore make it possible to channel the flow of gas F4 at the outlet of the turbojet engine 10.

The nozzle 28 further comprises an annular row of mobile external flaps 68 surrounding the assembly 38 of mobile internal flaps (FIG. 2) and articulated on the stator structure 50 of the turbojet engine so as to move in a synchronized manner with the assembly 38 of movable internal shutters.

In operation, the cooling air from the cooling plenum 36 escapes freely downstream and to the sides after having contributed to the cooling of the outer casing 32, and possibly contributes marginally to the cooling of the assembly. 38 mobile internal shutters.

The invention, a preferred embodiment of which will now be described with reference to FIGS. 4 to 8, proposes an improvement to the nozzle 28 of the convergent-divergent type with variable geometry. More specifically, the invention allows an improvement in the cooling of the assembly 38 of mobile internal flaps, as will appear more clearly in the following.

FIG. 4 more particularly shows a convergent flap-divergent follower flap pair 52B, as well as, arranged radially opposite the latter, a mobile external flap 68, illustrated very schematically. The explanations given below with reference to FIGS. 4 to 7 are valid for each of the follower convergent flap-divergent flap 52B pairs of the nozzle 28, and, preferably, also for each of the controlled convergent flap-divergent flap 52A pairs of the nozzle 28

The follower convergent flap-divergent flap pair 52B, also visible in FIGS. 4A to 7, comprises a convergent flap 40B and a divergent flap 42B.

As explained above, the divergent flap 42B is hinged at its upstream end 44 to the downstream end 46 of the convergent flap 40B, for example by means of a hinge joint 45, whereby the pair convergent flap-follower divergent flap 52B is able to pass from a first extreme angular configuration (FIG. 5A), in which the convergent flap 40B and the divergent flap 42B make between them a maximum salient angle, to a second extreme angular configuration (FIG. 5B), in which the convergent flap 40B and divergent flap 42B form between them a minimum salient angle less than the maximum salient angle.

Analogously to what is described above, the convergent flap 40B comprises a respective combustion gas channeling wall, called internal wall 56 in the following, extending in a respective longitudinal direction of the flap, and having, on a radially inner side, a respective internal combustion gas channeling surface 58, and, on a radially outer side, a respective outer surface 59.

Unlike the above, the convergent flap 40B comprises a respective external wall 60, extending opposite the external surface 59 of the internal wall 56 of this flap (FIGS. 4, 5A-5B and 7 ), for example parallel to the inner wall 56.

The convergent flap 40B further comprises two respective opposite side end walls 72 each connecting the internal wall 56 of this flap to the external wall 60 of this flap (FIGS. 6 and 7).

Thus, the convergent flap 40B comprises a respective cooling air circulation duct 70 (FIGS. 4, 5A-5B, 7) defined between the external surface 59 of the internal wall 56 of this flap and the external wall 60 of this flap. , and between the two side end walls 72 of this flap.

The cooling air circulation duct 70 of the convergent flap 40B comprises, at its upstream end, an end piece 73 (FIG. 4) configured to be connected to the cooling plenum 36 surrounding the postcombustion channel 26 (FIG. 2), so that the cooling air circulation duct 70 receives part of the cooling air flow CF1, in operation.

In addition, the cooling air circulation duct 70 is therefore delimited in particular by the outer surface 59 of the inner wall 56 of the flap (FIGS. 4, 5A-5B, 7). This last wall is thus cooled by air circulating in the cooling air circulation duct 70, in operation.

Analogously to what is described above, the divergent flap 42B comprises a respective combustion gas channeling wall 64, extending in a respective longitudinal direction of the flap, and having, on a radially internal side, a internal surface of respective combustion gas duct 66, and, on a radially outer side, a respective outer surface 67.

To facilitate the present description, an orthonormal reference X', Y', Z' is defined so that the direction X' corresponds to the longitudinal direction of the divergent flap 42B, and therefore in particular of the combustion gas channel wall 64 of the latter, and that the direction Y' corresponds to a transverse direction of the divergent flap, and the direction Z' corresponds to the direction of the thickness of the divergent flap.

Unlike the above, the divergent flap 42B further comprises a respective guide wall 76 extending opposite an upstream end portion of the combustion gas channeling wall 64 of this flap, so that these two walls 64 and 76 define between them a respective cooling air ejection duct 78 of the divergent flap 42B (FIGS. 4-7).

The diverging flap 42B further comprises two respective side end walls 80 each connecting the upstream end portion of the combustion gas channeling wall 64 to the guide wall 76 of the diverging flap (FIGS. 6 and 7), so that the two lateral end walls 80 laterally close (and therefore delimit between them) the cooling air ejection duct 78 of the divergent flap 42B.

The cooling air ejection duct 78 of the divergent flap 42B is connected to the cooling air circulation duct 70 of the convergent flap 40B (FIGS. 5A, 5B). The cooling air ejection duct 78 of the divergent flap 42B thus receives the flow of cooling air from the cooling air circulation duct 70 of the convergent flap 40B, or at least a majority part thereof , in operation, and allows this cooling air to be ejected along the internal combustion gas channeling surface 66 of the combustion gas channeling wall 64 of the diverging flap, as will appear more clearly in the following.

More specifically, the cooling air ejection duct 78 of the divergent flap 42B comprises for this purpose a respective connection portion 82 cooperating by fitting with a respective end portion 84 of the cooling air circulation duct 70 of the convergent flap 40B (FIGS. 4A, 5A-5B and 7).

In particular, the outer wall 60 of the convergent flap 40B comprises a respective main portion 85, for example of planar shape, and a respective end portion 86 which delimits a downstream part 84A of the end portion 84 of the circulation duct of cooling air 70 of the converging flap 40B (FIGS. 5A and 5B).

The end portion 86 is in the form of a portion of a cylinder of revolution with an axis coinciding with a pivot axis 87 about which the divergent flap 42B pivots with respect to the convergent flap 40B when the convergent flap-divergent follower flap 52B couple changes from one to the other of the first and second extreme angular configurations. In other words, the pivot axis 87 constitutes the axis of curvature of the end portion 86, the latter being concave when viewed from the pivot axis 87.

In the example illustrated, the hinge joint 45 has an outer surface 45A of cylindrical shape of revolution centered on the pivot axis 87 and in contact with the end portion 86 of the outer wall 60 of the convergent flap 40B ( Figures 5A-5B and 7).

The combustion gas channeling wall 64 of the divergent flap 42B comprises a respective main portion 89, for example of flat shape, and a respective end portion 88, which delimits the connection portion 82 of the air ejection duct cooling 78, and which is of complementary shape to the end portion 86 of the outer wall 60 of the converging flap 40B (FIGS. 5A and 5B). The end portion 88 of the combustion gas channeling wall 64 of the divergent flap 42B thus has the same axis of curvature as the end portion 86 of the outer wall 60 of the convergent flap 40B.

The curved shape of the end portions 86 and 88 allows a relative pivoting movement between the convergent flap 40B and the divergent flap 42B for the passage from one to the other of the first and second configurations of the convergent flap-divergent flap pair follower 52B.

The end portion 88 of the combustion gas channeling wall 64 of the divergent flap 42B is in surface contact with the end portion 86 of the outer wall 60 of the convergent flap 40B, such that the end portion 88 of the combustion gas channeling wall 64 slides along the end portion 86 of the outer wall 60, when the converging flap-diverging follower flap 52B pair passes from one to the other of the first and second extreme angular configurations (FIGS. 5A and 5B respectively).

Alternatively, these two walls may be spaced slightly apart, whereby the end portion 88 of the combustion gas conduit wall 64 moves opposite the end portion 86 of the wall. external 60 when switching from one to the other of the first and second configurations.

In the preferred embodiment illustrated, the connection portion 82 of the cooling air ejection duct 78 of the divergent flap 42B is engaged in the end portion 84 of the cooling air circulation duct 70 of the convergent flap 40B. In other words, the end portion 84 of the cooling air circulation duct 70 surrounds at least part of the connection portion 82 of the cooling air ejection duct 78.

The internal wall 56 of the convergent flap 40B has a planar shape including in a downstream end portion 90 of this wall, which downstream end portion delimits the downstream part 84A of the end portion 84 of the circulation duct of cooling air 70 of the converging flap 40B.

The guide wall 76 of the divergent flap 42B comprises a respective upstream portion 92 which delimits the connection portion 82 of the cooling air ejection duct 78 of the divergent flap 42B.

Seen in axial section, the upstream portion 92 is of homothetic shape to the shape of the end portion 88 of the combustion gas channeling wall 64 of the divergent flap, by a homothety whose center is located on the axis of pivot 87. The upstream portion 92 thus also has an axis of curvature coincident with the pivot axis 87. By "axial section", it is necessary to understand a section according to a plane comprising the longitudinal axis 11 of the turbojet engine, that is to say that is, along a plane orthogonal to the combustion gas channeling wall 64 of the diverging flap 42B and to the pivot axis 87.

The upstream portion 92 of the guide wall 76 of the divergent flap 42B can thus move facing the downstream end portion 90 of the combustion gas channeling wall 56 of the convergent flap 40B when the convergent flap-divergent flap pair follower 52B passes from one to the other of the first and second extreme angular configurations.

The connection portion 82 of the cooling air ejection duct 78 of the divergent flap 42B and the end portion 84 of the cooling air circulation duct 70 of the convergent flap 40B are configured so that possible leaks of air LF between the cooling air circulation duct 70 and the cooling air ejection duct 78 are located between the upstream portion 92 of the guide wall 76 of the divergent flap 42B and the downstream end portion 90 of the combustion gas channeling wall 56 of the converging flap 40B.

In the example illustrated, this feature is obtained, on the one hand, thanks to the contact between the end portion 88 of the combustion gas channeling wall 64 of the divergent flap 42B and the end portion 86 of the wall external 60 of the convergent flap 40B, which prevents air leaks between these two walls, and on the other hand, by means of a slight clearance between the upstream portion 92 of the guide wall 76 of the divergent flap 42B and the portion downstream end 90 of the combustion gas channeling wall 56 of the converging flap 40B.

Thus, any air leaks LF between the cooling air circulation duct 70 of the convergent flap 40B and the cooling air ejection duct 78 of the divergent flap 42B occur in the same direction as the flow. of the flow of gas F4 coming from the post-combustion channel 26. The pressure drops induced by any air leaks LF are thus minimized. In addition, these possible air leaks LF can thus form a cooling film along the combustion gas channeling surface 66 of the divergent flap 42B, and thus contribute to the cooling of the divergent flap 42B.

In addition, the outer wall 60 of the converging flap 40B comprises a bulge 94 adjacent to the end portion 86 of this outer wall 60, the bulge being shaped so as to present an inner surface 94A of concave shape and an outer surface 94B of convex shape. By "internal surface", it is necessary to understand a surface delimiting the cooling air circulation duct 70 of the converging flap 40B. By "external surface" is meant a surface external to said conduit. The bulge 94 delimits an upstream part 84B of the end portion 84 of the cooling air circulation duct 70 of the convergent flap 40B. The bulge 94 and the end portion 86 of the outer wall 60 of the converging flap together present a wave shape.

The bulge 94 makes it possible to orient the flow of cooling air CF1 substantially orthogonally to an inlet section 96 of the connection portion 82 of the cooling air ejection duct 78 of the divergent flap 42B (FIGS. 5A and 5B ).

Furthermore, the cooling air ejection duct 78 of the divergent flap 42B comprises an air outlet portion 98 arranged in the extension of the connection portion 92 and having an air outlet section 99 (FIG. 4A , 5A and 5B) remote from a downstream end 64A of the flue gas channel wall 64 of the diverging flap (FIG. 4), to eject the cooling air along the internal surface of the flue gas channel 66 of the combustion gas duct wall of the diverging damper, in operation.

The distance L between the air outlet section 99 and the downstream end 98A of the flue gas channel wall 64 of the diverging flap is preferably greater than 50% of the overall longitudinal extent E of the channel wall. combustion gas 64, even more preferably greater than 75% of this overall longitudinal extent E, and even more preferably greater than 90% of the overall longitudinal extent E.

In the preferred embodiment described, the air outlet portion 98 of the cooling air ejection duct 78 of the divergent flap comprises or, in the example described, forms, a sonic throat. The air outlet portion 98 thus makes it possible to accelerate beyond Mach 1 the cooling air coming from the cooling air circulation duct 70 of the divergent flap 40B, at least for a critical point of the range of operating regimes with turbojet afterburner.

More specifically, the combustion gas channeling wall 64 of the divergent flap 42B comprises a sonic neck portion 98A connecting the main portion 89 of this wall to the end portion 88 of this wall. The guide wall 76 of the divergent flap 42B includes a sonic neck portion 98B in the extension of the upstream portion 92 of this wall. The sonic neck portions 98A and 98B diverge from each other in the downstream direction and are aerodynamically curved. In particular, seen from inside the duct 78, each sonic neck portion 98A, 98B comprises a respective convex upstream part, and a respective concave downstream part, separated from each other by a line of inflection.

Furthermore, in the embodiment described, the converging flap 40B further comprises a multi-perforated plate 102 extending between the internal wall 56 and the external wall 60 of the converging flap, and provided with impact cooling orifices 104 (figures 4A and 5A).

The multi-perforated plate 102 divides the cooling air circulation duct 70 of the converging flap 40B into a cooling air circulation cavity 105 defined between the external wall 60 and the multi-perforated plate 102 and communicating directly with the end piece 73 of the duct, and an impact cooling cavity 106 defined between the multiperforated plate 102 and the external surface 59 of the internal wall 56 of this shutter, to allow cooling of this wall 56 by impact of air jets formed through the orifices cooling by impact 104 from air circulating in the cooling air circulation cavity 105.

To this end, the multiperforated plate 102 preferably extends at a short distance from the outer surface 59 of the inner wall 56, for example at a distance of approximately 1 mm from the latter.

The cooling air flow CF1 circulating in the cooling air circulation cavity 105 thus enters the impact cooling cavity 106 by forming impact jets IJ through the impact cooling orifices 104 of the plate. multiperforated 102, in operation. The IJ impact jets allow optimal cooling of the internal wall 56.

The convergent flap 40B further comprises a closure wall 112 connecting the multi-perforated plate 102 to the internal wall 56 so as to close an upstream end of the impact cooling cavity 106 and thus separate the latter from an upstream end part of the cooling air circulation cavity 105.

Such a closure wall 112 makes it possible in particular to prevent air from entering the impact cooling cavity 106 from the upstream side without passing through orifices 104 of the multiperforated plate, and to avoid recirculation of the air after it has passed through the orifices 104 of the multiperforated plate 102.

The impact cooling orifices 104 are advantageously staggered (FIG. 8). The longitudinal pitch E1 between two rows of orifices and the lateral pitch E2 between orifices within each row are for example each equal to 1 cm, while the diameter of each orifice 104 is for example equal to 1 mm.

Furthermore, the multi-perforated plate 102 has a downstream end 102A remote from the connection portion 82 of the cooling air ejection duct 78, so as to form an opening 114 at the downstream end of the impact cooling cavity. 106 allowing the air circulating in the impact cooling cavity 106 to escape therefrom and enter the connecting portion 82 of the cooling air ejection duct 78.

In operation, the gas flow F4, consisting of the mixture of combustion gases from the primary stream, and the secondary flow F3, circulates in the post-combustion channel 26, then escapes from the turbojet engine 10 through the nozzle 28 , as explained above with reference to Figure 2.

The cooling air flow CF1 circulates along the outer casing 32 within the cooling plenum 36 (FIG. 2) then enters the cooling air circulation duct 70 of a convergent flap 40B through the tip 73 of the latter (Figure 4).

The flow of cooling air CF1 circulates in the cooling air circulation duct 70 up to the end portion 84 of the latter, thus cooling the converging flap 40B, in particular the gas channeling wall of combustion 56 of this flap. To this end, part of the air flow CF1 passes through the impact cooling orifices 104 of the multiperforated plate 102 by forming the impact jets IJ (FIGS. 4A and 5A), then joins the end portion 84 passing through the opening 114 of the impact cooling cavity 106.

Then the cooling air flow CF1 enters the cooling air ejection duct 78 of the corresponding divergent flap 42B via the connection portion 82 of the latter.

The cooling air flow CF1 is then ejected through the air outlet section 99 of the cooling air ejection duct 78, and thus forms a film of cooling air CAF1 along the surface. internal combustion gas channeling 66 of the combustion gas channeling wall 64 of the diverging flap 42B, allowing effective cooling of the latter.

In the embodiment described, the flow of cooling air CF1 is accelerated to supersonic speed by passing through the sonic throat 98 before being ejected through the air outlet section 99 of the duct. cooling air ejection 78. The cooling air film CAF1 thus has a speed close to that of the flow of gas F4 circulating in the nozzle 28, which is beneficial for the general performance of the turbojet engine.

In embodiments of the invention, the cooling methods described above with regard to the follower convergent flap-divergent flap pairs 52B are also valid with regard to the controlled convergent flap-divergent flap pairs 52A.

In other embodiments of the invention, the controlled convergent flap-divergent flap couples 52A have different characteristics, and comprise for example divergent flaps devoid of a cooling air ejection duct, and optionally, flaps converging without a cooling air flow channeling duct. The controlled flaps are in fact generally less exposed to the heat of the combustion gases than the follower flaps. For example, in FIG. 3, it is clear that each follower divergent flap 42B has lateral end portions 42B-L extending respectively in front of respective lateral end portions 42A-L of the two adjacent controlled divergent flaps 42A, and thus mask these respective lateral end portions of the controlled divergent flaps 42A vis-à-vis the combustion gases. Thus, only a respective middle part 42A-M of each controlled divergent flap 42A is directly exposed to the combustion gases.

In general, the invention is applicable to any type of turbojet comprising a nozzle of the convergent-divergent type with variable geometry, and in particular of the type further comprising a postcombustion channel upstream of said nozzle.

Claims (11)

Convergent-divergent flap (52B) pair for nozzle (28) of a convergent-divergent turbojet engine with variable geometry, comprising a convergent flap (40B), and a divergent flap (42B) pivotally mounted on the convergent flap around a pivot axis (87), whereby the converging flap-diverging flap couple is capable of passing from a first extreme angular configuration, in which the converging flap and the diverging flap form between them a maximum salient angle, to a second angular configuration extreme, in which the converging flap and the diverging flap make between them a minimum salient angle less than the maximum salient angle,
wherein the converging flap (40B) has a respective inner wall (56), having a respective combustion gas channeling inner surface (58) and a respective outer surface (59), and a respective outer wall (60),
wherein the convergent louver (40B) includes a respective cooling airflow duct (70) defined between the respective outer surface (59) of the respective inner wall of the convergent louver, and the respective outer wall (60) of the louver convergent,
wherein the diverging flap (42B) has a respective flue gas channeling wall (64), having a respective flue gas channeling inner surface (66) and a respective outer surface (67), and
wherein the diverging flap (42B) further comprises a respective cooling air ejection duct (78) connected to the respective cooling air circulation duct (70) of the converging flap (40B) for receiving cooling air therefrom, and configured to eject the cooling air along the respective combustion gas channeling inner surface (66) of the respective combustion gas channeling wall (64) of the diverging flap ( 42B). Converging flap-diverging flap pair according to claim 1, in which the respective cooling air ejection duct (78) of the divergent flap (42B) comprises:
- a respective connection portion (82) cooperating by fitting with a respective end portion (84) of the respective cooling air circulation duct (70) of the convergent flap (40B) so as to ensure the connection of the duct ejection of cooling air (78) respective from the diverging flap to the cooling air circulation duct (70) respective from the converging flap, and
- an air outlet portion (98) arranged in the extension of the connection portion (82) and having an air outlet section (99) remote from a downstream end (64A) of the respective flue gas duct (64) of the diverging flap (42B) to eject cooling air along the respective flue gas duct (66) inner surface of the respective flue gas duct wall (64) of the diverging flap (42B). Converging flap-diverging flap pair according to claim 2, in which:
- the respective outer wall (60) of the convergent flap (40B) comprises a respective end portion (86) which delimits a downstream part (84A) of the end portion (84) of the cooling air circulation duct (70) of the convergent flap, and which is in the form of a cylinder portion with an axis merging with the pivot axis (87), and
- the respective combustion gas channeling wall (64) of the divergent flap (42B) comprises a respective end portion (88), which delimits the connection portion (82) of the cooling air ejection duct ( 78) of the divergent flap, and which is of complementary shape to the respective end portion (86) of the respective outer wall (60) of the convergent flap, such that the respective end portion (88) of the respective combustion gas channel wall (64) of the diverging flap slides along, or moves opposite, the respective end portion (86) of the respective outer wall (60) of the diverging flap, when the torque convergent flap-divergent flap passes from one to the other of the first and second extreme angular configurations. Converging flap-diverging flap pair according to claim 3, in which the connection portion (82) of the respective cooling air ejection duct (78) of the divergent flap (42B) is engaged in the end portion (84 ) of the cooling air circulation duct (70) of the respective converging flap (40B). Converging flap-diverging flap pair according to claim 4, in which the respective external wall (60) of the converging flap (40B) comprises a bulge (94) adjacent to the end portion (86) of the respective external wall (60). of the converging flap, the bulge (94) being of inverted concavity with respect to the respective end portion (86) of the respective outer wall of the converging flap, and the bulge (94) delimiting an upstream part (84B) of the end (84) of the respective cooling air circulation duct (70) of the converging flap. Converging flap-diverging flap pair according to any one of Claims 2 to 5, in which the air outlet portion (98) of the respective cooling air ejection duct (78) of the divergent flap (42B) comprises or forms a sonic saddle. Converging flap-diverging flap pair according to any one of Claims 1 to 6, in which the converging flap (40B) further comprises a multiperforated plate (102) extending between the respective internal wall (56) and the external wall ( 60) of the converging flap, and provided with impact cooling orifices (104), and
wherein the respective cooling air circulation duct (70) of the converging flap comprises:
- a cooling air circulation cavity (105) defined between the respective outer wall (60) of the converging flap and the multi-perforated plate (102), and
- an impact cooling cavity (106) defined between the multi-perforated plate (102) and the respective outer surface (59) of the respective inner wall (56) of the convergent flap, to allow cooling of the respective inner wall (56) of the converging flap by impact of air jets (IJ) formed through the impact cooling orifices (104) from air (CF) circulating in the cooling air circulation cavity (105). Converging flap-diverging flap pair according to claim 7, in which the converging flap (40B) comprises two respective opposite lateral end walls (72) each connecting the respective internal wall (56) of the converging flap to the external wall (60) of the converging flap so that the two lateral end walls (80) delimit between them the respective cooling air circulation duct (70) of the converging flap. Converging shutter-diverging shutter couple according to claim 7 or 8, in which the converging shutter (40B) comprises a closing wall (112) connecting the multiperforated plate (102) of the converging shutter to the respective internal wall (56) of the converging shutter so as to close an upstream end of the impact cooling cavity (106). Nozzle (28) of the convergent-divergent type with variable geometry for a turbojet, comprising convergent-divergent flap pairs distributed around an axis (11) of the nozzle and at least some of which are convergent-divergent flap pairs along the any one of claims 1 to 9, and a combustion gas circulation channel (39) delimited at least by the respective internal combustion gas channeling surfaces (58, 66) of the respective internal walls of the converging flaps (40B) respective diverging flaps (42B) of the converging flap-diverging flap pairs according to any one of claims 1 to 9. Turbojet engine for aircraft, comprising a postcombustion channel (26) surrounded by a cooling plenum (36) separated from the postcombustion channel (26) by a thermal protection jacket (34), and a nozzle (28) according to claim 10 ,
wherein the respective cooling air circulation ducts (70) of the convergent flaps (40B) of the convergent flap-divergent flap pairs (52B) according to any one of claims 1 to 9 of the nozzle (28) are connected to the cooling plenum (36) surrounding the afterburner channel (26).